On Tue, Sep 25, 2012 at 12:32:37PM +0300, Tero Kristo wrote:
> diff --git a/arch/arm/mach-omap2/powerdomain.c
> b/arch/arm/mach-omap2/powerdomain.c
> index ba49029..ca54aec 100644
> --- a/arch/arm/mach-omap2/powerdomain.c
> +++ b/arch/arm/mach-omap2/powerdomain.c
> @@ -1475,10 +1477,16 @@ int pwrdm_state_switch(struct powerdomain *pwrdm)
> */
> void pwrdm_clkdm_enable(struct powerdomain *pwrdm)
> {
> + unsigned long flags;
> +
> if (!pwrdm)
> return;
>
> - atomic_inc(&pwrdm->usecount);
> + if (atomic_inc_return(&pwrdm->usecount) == 1) {
> + spin_lock_irqsave(&pwrdm->lock, flags);
> + voltdm_pwrdm_enable(pwrdm->voltdm.ptr);
> + spin_unlock_irqrestore(&pwrdm->lock, flags);
> + }
This looks like the classic "I like atomic types because they have magic
properties" brain-deadness.
What would happen to users of this if you had this sequence:
pwrdm->usecount starts off as 1.
Thread0 Thread1
atomic_inc_return() (returns 1)
atomic_inc_return() (returns 2)
starts using stuff in power domain
spin_lock_irqsave()
voltdm_pwrdm_enable()
spin_unlock_irqrestore()
?
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